Advanced Receive System and RSPduo Integration

The ON7MV remote station includes a dedicated receive system built around two remotely controlled RX antenna switches, an SDRplay RSPduo and the Icom IC-7600. The purpose of this system is to give the operator full control over the receive antennas while keeping the operation clear, safe and repeatable.

Each RX switch can select one of several receiving antennas. The selected antenna can be routed to the RSPduo or, when required, to the separate receive input of the IC-7600. All switching is controlled through the ON7MV cockpit and the current status is shared between connected users. This means that every operator sees the same antenna selection and the same active receive source.

A major reason for building this system was to reduce operating mistakes. During contests or DX operation, several antennas, receivers and signal paths may be available at the same time. Manual switching can easily lead to a wrong antenna selection, an incorrect signal route or confusion between operators. The central Raspberry Pi control system makes the selection process more predictable and prevents different users from unknowingly working with conflicting settings.

Safety was an important part of the design. The RX paths use controlled relay switching, with only one input selected at a time. When changing antennas, the system first disconnects the existing selection before activating the next one. Additional safety relays protect the sensitive receive equipment when the station transmits. This is especially important in a high-power amateur radio station, where the RSPduo and the receive antenna system must be isolated from transmitted RF.

What is the RSPduo?

The SDRplay RSPduo is a software-defined radio receiver with two independent tuners. Unlike a traditional receiver, much of its operation is performed through software. It can display a wide part of the radio spectrum, show multiple signals at the same time and provide detailed control over filters, modes, audio and signal analysis.

At ON7MV, the RSPduo is connected to the Raspberry Pi and is operated through SDRconnect. The receive antennas themselves are selected through the ON7MV cockpit, while SDRconnect is used for the spectrum display, tuning, demodulation and audio processing.

The RSPduo can be used as a normal single-tuner receiver, but one of its most important features is diversity reception.

Diversity Reception

Diversity reception uses both RSPduo tuners at the same time. Each tuner receives the same frequency, but from a different antenna or receive path. The two signals can then be combined in software.

Because noise, interference and fading are not always identical on both antennas, the signals can be adjusted in phase and amplitude. This can reduce an unwanted signal or local noise while improving the wanted DX station. In other situations, diversity can reduce fading and make a weak signal more stable and easier to understand.

The best results are obtained when the two receive antennas hear the signal differently. For example, one antenna may receive the wanted station more clearly, while another receives less interference. Diversity reception uses the difference between both signals to improve the final result.

Practical Advantages

The complete RX system offers several important advantages:

• remote selection of multiple receiving antennas;

• direct control of both RSPduo tuners;

• a shared and clearly visible station status;

• safer switching during high-power operation;

• reduced risk of operator mistakes;

• improved weak-signal reception;

• better suppression of interference and local noise;

• diversity reception for difficult DX and contest signals.

The RX system is fully integrated into the wider ON7MV remote station. The cockpit screens show the selected RX antennas, the RX9 direction, the RSPduo tuner selections and the active receive source. The individual control screens can be seen on the Remote Station 2026 page of this website.

This project is not only intended to make remote operation possible. Its main purpose is to make a complex station easier, safer and more consistent to operate, both for the station owner and for visiting contest operators.